In Christopher Nolan’s new movie, humanity’s hope for survival is pinned on one man: Matthew McConaughey, pilot of a last-ditch mission to find humans a new home as Earth becomes uninhabitable. And in turn, Interstellar, which opens worldwide on 7 November, heads towards cinemas heavy with expectations.

In a year strikingly light on both critical and commercial hits, it’s down to this three-hour Imax epic to save cinema as the clock ticks on the last quarter. Nolan has millions of devoted fans from his Batman trilogy, plus the rare clout to get studio backing for adult blockbusters which don’t feature superheroes. Early screenings have attracted very warm reviews, Oscar buzz and comparisons to Kubrick’s 2001, whose extended deep space sequences Nolan appears to ape.

Yet at a press conference in London on Wednesday, Nolan said his key inspiration was films such as Close Encounters of a Third Kind, which sought to speculate about a moment when humans would need to reassess their place in the cosmos.

Interstellar does so from a post-climate change perspective. It shows a world decimated by a man-made agricultural blight that forces other options to be scoped out. Rather than being a call to arms to preserve the planet, it fast-forwards to a time when any such battle has been lost.

“It has as a jumping-off point not that we’re meant to save the earth, we’re meant to leave it,” said Nolan. “Obviously, if that’s taken literally it would not be particularly positive. The film feeds off certain concerns that are very valid in the world today. But really it’s about saying what is mankind’s place in the universe? I think it’s very exciting to deal with that dramatically and I think it’s important we have to deal with that out of necessity. In real life, it would be far better if we dealt with that issue out of choice.”

McConaughey’s character is mentored by a man played by Michael Caine and loosely based on the astrophysicist Kip Thorne. Thorne’s work both inspired and informed the film, but Caine, 81, said that until he spoke with the scientist, the only wormholes he’d been familiar with were those in his garden.

Caine, who has now worked with Nolan six times, said his own re-evaluation of the reality of climate change coincided with his making the film. “When I went to do this movie in LA two years ago I left on 2 October. It was 86 degrees here and when I got to Los Angeles it was pouring with rain. That is the exact opposite of what it’s supposed to be. That worried me. I’d never believed in global warming and I went: ‘Whoops. Maybe there is something in it.’”

Asked if he was taking measures to try reduce his own ecological footprint, Caine jokingly protested that he was still making up for a frugal youth. “I was so poor for so long. I didn’t use anything or eat very much so I figured the world owed me a debt. Now I’ve been eating very well and have had a big car for a long time.”

His fellow cast-members banged the ecological drum a little harder, with vegan Jessica Chastain championing “meat-free Mondays” and Anne Hathaway saying she timed her showers and tried to support small, ethical businesses. Nolan, meanwhile, expressed enthusiasm for pooling resources, “gathering people in one place, like a movie theatre – you can save an enormous amount of electricity”.

Interstellar suggests the survival of the species may depend on enough people extending a sense of empathy beyond their immediate family. It acts as a tribute to those adventurers of the past who were able to sideline short-termism in the service of exploration. But the cast agreed what would be needed to prevent such action from becoming necessary in the first place was a rapid and concerted effort.

“I think mother nature’s gonna be just fine,” said McConaughey. “But we might not. The masses have to have a personal stake in things to take action.”

Hathaway pointed to societal structures as a cause of such inertia. “I don’t think we’ve learned how to broach with the topic with your average person that your life is being controlled by a small group of people who are themselves controlled by greed.”

Both actors, as well as Chastain and Nolan, reported that they nonetheless remained optimistic, and had faith in the sentiment of the film’s tagline: “The end of Earth will not be the end of us.”

Caine, however, remained sceptical. “If Earth screws up, I think we all go,” he said. “How many people can go through a black hole in a rocket? It’s not a bus.”

The long read: He is one of the few directors who can walk into a Hollywood studio with an idea and come out with $200m. So, asks Tom Shone, will Nolan’s latest epic, Interstellar, reinforce his reputation as the auteur who thinks big?

The stars of Christopher Nolan's sci-fi epic, about a mission to find a new home away from ecologically-ravaged earth, talk to Catherine Shoard about climate change, human endeavour and getting tangled up in string theory